The Perseid meteor shower has begun. Although the display will not peak until August 12th and 13th, sky watchers are already counting as many as a dozen meteors per hour (including some nice fireballs) during the darkest hours before dawn. Rates could increase 5- to 10-fold when the shower reaches maximum on Sunday night and Monday morning. Advice: Get away from city lights. While many Perseids will be bright enough to see from light-polluted urban areas, the shower's full grandeur is reserved for places with dark and starry skies. This is a good weekend to go camping.

Visit http://Spaceweather.com for photos, observing tips and a sky map. Full coverage of the shower begins today and will continue until Perseid activity subsides.

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On Sept. 1st, a flurry of bright and oddly-colored meteors could spill across the skies of western North America--or not. Forecasters are divided about what will happen next month when Earth runs into an ancient stream of debris from mysterious Comet Kiess.

Astronomers have discovered something they've never seen before: a star with a tail like a comet. Even more amazing is the fact that the newfound tail is attached to one of the most popular stars in the sky, a red giant named Mira. Amateur and professional astronomers have been watching Mira for 400 years and only recently has a NASA space telescope spotted its massive tail.

On Aug. 20th, an amateur astronomer in Oklahoma scanned the sky for meteors using a low-light video camera--but instead of meteors, he recorded a bizarre upside-down form of lightning called "Gigantic Jets." Discovered in 2001, Gigantic Jets are enormous discharges that leap upward 50 miles high from the tops of thunderclouds. They are related to better known sprites and elves, but are larger and more dramatic. The Oklahoma Jets are the first ever photographed over the continental United States and they may provide key data to researchers working to understand the phenomenon. Visit http://spaceweather.com to view a movie of the Jets and to learn how you might be able to catch them yourself.

mariaAdministrateur Messages postés : 20960

Posté le 25/08/2007 11:02:02

ASTRONOMERS PUZZLED BY COSMIC BLACK HOLE

Aug 23, 11:03 PM (ET)By SETH BORENSTEIN

WASHINGTON (AP) - Astronomers have stumbled upon a tremendous hole in the universe. That's got them scratching their heads about what's just not there. The cosmic blank spot has no stray stars, no galaxies, no sucking black holes, not even mysterious dark matter. It is 1 billion light years across of nothing. That's an expanse of nearly 6 billion trillion miles of emptiness, a University of Minnesota team announced Thursday.

Astronomers have known for many years that there are patches in the universe where nobody's home. In fact, one such place is practically a neighbor, a mere 2 million light years away. But what the Minnesota team discovered, using two different types of astronomical observations, is a void that's far bigger than scientists ever imagined.

"This is 1,000 times the volume of what we sort of expected to see in terms of a typical void," said Minnesota astronomy professor Lawrence Rudnick, author of the paper that will be published in Astrophysical Journal. "It's not clear that we have the right word yet ... This is too much of a surprise."

Rudnick was examining a sky survey from the National Radio Astronomy Observatory, which essentially takes radio pictures of a broad expanse of the universe. But one area of the universe had radio pictures indicating there was up to 45 percent less matter in that region, Rudnick said.

The rest of the matter in the radio pictures can be explained as stars and other cosmic structures between here and the void, which is about 5 to 10 billion light years away.

Rudnick then checked observations of cosmic microwave backgroundradiation and found a cold spot. The only explanation, Rudnick said, is it's empty of matter.

It could also be a statistical freak of nature, but that's probably less likely than a giant void, said James Condon, an astronomer at the National Radio Astronomy Observatory. He wasn't part of Rudnick's team but is following up on the research.

"It looks like something to be taken seriously," said Brent Tully, a University of Hawaii astronomer who wasn't part of this research but studies the void closer to Earth.

Tully said astronomers may eventually find a few cosmic structures in the void, but it would still be nearly empty.

Holes in the universe probably occur when the gravity from areas with bigger mass pull matter from less dense areas, Tully said. After 13 billion years "they are losing out in the battle to where there are larger concentrations of matter," he said.

Retired NASA astronomer Steve Maran said of the discovery: "This is incredibly important for something where there is nothing to it."

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On the Net:

Rudnick paper: http://xxx.lanl.gov/pdf/0704.0908

National Radio Astronomy Observatory: http://www.nrao.edu/pr/2007/coldspot/

Last week in Boulder, Colorado, scientists converged on the "Living With A Star" workshop to share the latest research in solar physics. At one point, nearly 200 participants sat slack-jawed as they watched a new movie recorded by Japan's Hinode spacecraft showing a sunspot emerging from the depths of the sun. The newborn spot resembled nothing less than a swimming planet-sized trilobite. See for yourself--and find out what it means--in today's Science@NASA story.

NASA's Mars orbiters have spotted "skylights" apparently leading to cavernous underground spaces on Mars. The discovery is fueling interest in potential underground habitats and sparking searches for caverns elsewhere on the Red Planet.

CELESTIAL TRIANGLE: Set your alarm. For the next five mornings, just before dawn banishes the night, you can see a compact celestial triangle rising in the eastern sky. The corners are dazzling Venus, Saturn and the bright star Regulus. This is worth waking up for--at least once.

Visit http://spaceweather.com for sky maps and more. AURORA WATCH: A solar wind stream is heading for Earth and it may spark a geomagnetic storm when it arrives on Oct. 11th or 12th. High-latitude sky watchers should be alert for auroras.

ERUPTING COMET: Astronomers in Japan and Europe report that Comet 17P/Holmes is undergoing a spectacular eruption. The 17th-magnitude comet has brightened by a factor of five hundred thousand or more during the past 24 hours becoming a naked eye object in the evening sky. This may signify a breakup of the comet's core or a rich vein of ice suddenly exposed to sunlight--no one knows. Look for a yellow 2.5th-magnitude fuzzball in the constellation Perseus after sunset. ("2.5th magnitude" means a little dimmer than the stars of the Big Dipper.) At present the comet looks more like a star than a comet; it does not have a discernable tail, but it might grow one as the outburst continues. Visit http://spaceweather.com for a sky map, photos and updates.

COMET TAIL: Exploding Comet 17P/Holmes continues to amaze onlookers. On Nov. 8th and 9th part of the comet's blue tail broke away in view of many backyard telescopes. Visithttp://spaceweather.com to see photos of the "disconnection event" and speculation about what might have caused it.

TAURID METEOR SHOWER: The annual Northern Taurid meteor shower caused by Comet Encke peaks on Nov. 12th. Although Taurid rates are normally low, only about five meteors per hour, those five can be doozies. The shower is a well-known producer of slow, bright fireballs visible at all hours of the night. If you're outside after dark this weekend, be alert for Taurids.

mariaAdministrateur Messages postés : 20960

Posté le 15/11/2007 07:01:21

Space Weather News for Nov. 15, 2007

GIANT COMET: University of Hawaii astronomers have measured the diameter of Comet 17P/Holmes: 1.4 million kilometers. This makes the exploding comet bigger than the sun and now the largest object in the solar system. Not surprisingly, the comet is visible to the naked eye; with only a backyard telescope you can watch its gigantic debris cloud expand from night to night. Nov. 19th is an especially good night to look: Comet Holmes will glide by Mirfak, the brightest star in the constellation Perseus, and appear to swallow it.

NASA's fleet of THEMIS satellites has made some surprising new discoveries about outbursts of Northern Lights and the source of their power. Findings include giant magnetic ropes that connect Earth to the Sun and explosions in the outskirts of Earth's magnetic field.

The solar physics community is abuzz this week. No, there haven't been any great eruptions or solar storms. The source of the excitement is a modest knot of magnetism that popped up on the sun, possibly heralding the start of a new solar cycle.

CLOSE ENCOUNTER WITH MARS: Have you noticed an intense red star rising in the east in recent evenings? That's no star, that's Mars. The red planet is having a close encounter with Earth this week. At closest approach on Tuesday evening, Dec. 18th, the two worlds will lie only 55 million miles apart. Mars won't be this nearby again until the year 2016. To the naked eye, Mars now outshines every star in the night sky (it is slightly brighter than Sirius) and it looks great through a backyard telescope. Visit http://spaceweather.com for photos, observing tips and sky maps.

NOTE: While, technically speaking, Mars is at its best and brightest only on Dec. 18th, the red planet will remain unusually close and beautiful for weeks to come. This makes it a Merry Martian Christmas for anyone who finds a telescope under their tree on Dec. 25th: http://spaceweather.com/ccount.php?linkURL=http://meade.com

GREAT GEMINIDS: The Geminid meteor shower peaked on Dec. 14th and 15th; as predicted, it was a great show. Some observers counted more than a hundred meteors per hour including fireballs that cast shadows like a full moon and gave off ghostly-sounding radio echoes. It's all chronicled in our Geminid Gallery: http://spaceweather.com/meteors/gallery_14dec07_page4.htm

URSID METEORS: Earth is heading for a stream of comet dust that could produce a pleasing outburst of "shooting stars" this weekend. Forecasters say dozens of meteors per hour could emerge from a spot in the sky near the North Star (Polaris) when Earth encounters the dust on Saturday evening, Dec. 22nd. These meteors are called "Ursids" after Ursa Minor, the constellation where the North Star is located. If forecasting models are correct, the shower's peak will occur between 2100 and 2200 UT (4-5 pm EST) with meteors visible as much as four hours before and after that time.

The source of the dust is Comet 8P/Tuttle, which is traveling through the inner solar system this month and next. The comet itself can be seen through binoculars not far from the radiant of the shower. This gives sky watchers a rare opportunity to see a comet and its meteors in the same observing session.

Ursid meteors, which appear in small numbers annually, have a reputation for faintness and delicacy. Dark skies are usually required to see them; bright moonlight on Dec. 22nd will only exacerbate the problem of visibility. However, say forecasters, during an outburst of Ursids there may be a fair number of bright meteors. No one knows what will happen--all the more reason to look!

MOON AND MARS: Please don't miss this: At sunset on Sunday, Dec. 23rd, the full Moon and Mars will rise in the east less than two degrees apart. So close together, the two brightest objects in the evening sky look absolutely dynamite. The display will be visible all night long, even from brightly lit cities, and requires no telescope to enjoy.

URSID UPDATE: Observers in Europe report a modest outburst of Ursid meteors last night. The intensity and timing of the flurry is in good accord with predictions that Earth would run into a stream of dust from Comet 8P/Tuttle on Dec. 22nd. Now that the meteor shower is over, attention turns to the comet itself. After a 13.6 year absence, 8P/Tuttle is once again traveling through the inner solar system. At closest approach to Earth on Jan. 1st and 2nd, 2008, the comet, will brighten to 5th or 6th magnitude--a fine target for backyard telescopes and digital cameras.

SOLAR ACTIVITY: The New Year could begin with a bang--or rather a solar flare. A sunspot hidden just behind the sun's eastern limb has unleashed two X-ray flares and a bright CME (coronal mass ejection) in the past 24 hours. This activity could signal the return of large sunspot 978, which has spent the last two weeks transiting the far side of the sun. Today or tomorrow, the sun's rotation should carry the active region over the limb and into view from Earth; then we can evaluate its potential for more flares and CMEs. Visit http://spaceweather.com for images and updates.

HEAVENLY MEETING: Last night, emerald Comet 8P/Tuttle glided by spiral galaxy M33 producing a heavenly scene for astrophotographers around the world. Dozens of photos may be found in Spaceweather's Comet Tuttle gallery: http://spaceweather.com/comets/gallery_tuttle_page4.htm